This invention relates to a process for preparing linearly-extended polyalkylenepolyamines, such as diethylenetriamine, and linear and branched triethylenetetramines.
Linearly-extended polyalkylenepolyamines find utility as dispersants, surfactants, chelants, catalysts, curing agents, extenders in polyurethanes, and as starting materials in the preparation of pesticides.
It is known that non-cyclic polyalkylenepolyamines can be prepared by the reaction of an alkyl halide with ammonia or an amine. The product is a polyalkylenepolyamine hydrohalide salt, which must be neutralized with base in order to recover the valuable polyalkylenepolyamine product. The neutralization produces a waste stream of metal salt which must be removed. Moreover, the process produces considerable amounts of undesirable cyclic products.
Certain patents teach the reforming of alkylenepolyamines, such as ethylenediamine, directly to non-cyclic polyalkylenepolyamines. For example, U.S. Pat. No. 4,316,841 discloses such a process with a catalyst of boron phosphate, a phosphate of a Group IA or IIA metal, or a phosphate of zirconium, antimony, tin or iron. These catalysts are soluble in amines and water. Consequently, they leach into the reaction causing catalyst losses and separation problems.
U.S. Pat. No. 3,956,329 discloses the deammoniation of an alkyleneamine or an aminoethylpiperazine over a zeolite catalyst containing at least one cation selected from the alkali metals, the alkaline earth metals, zinc group elements, hydrogen and ammonium cations. Disadvantageously, this process produces large amounts of undesirable cyclic materials, such as triethylenediamine and piperazine.
U.S. Pat. No. 4,547,591 discloses the preparation of predominantly linear polyethylenepolyamines by reforming ethyleneamines in the presence of a silica-alumina catalyst. Optionally, the catalyst contains an acidic phosphorus cocatalyst. This process produces considerable quantities of undesirable cyclic materials, such as piperazines.
U.S. Pat. No. 4,568,746 teaches a process of reforming ethylenediamine in the presence of a catalyst containing nickel, cobalt or rhodium. Likewise, U.S. Pat. No. 4,625,030 teaches a process of contacting ethylenediamine in the presence of hydrogen with a catalyst comprising nickel impregnated or coated together with iridium or platinum on a support of silica-alumina. These processes are limited to the preparation of diethylenetriamine, and do not produce higher homologues. Moreover, these processes require hydrogen and an expensive noble metal.
It would be desirable to have an inexpensive catalyst which is capable of reforming alkylenepolyamines directly to polyalkylenepolyamines without the formation of undersirable by-products, such as water. It would be more desirable if such a catalyst was insoluble in amines and water, so as to avoid catalyst losses and separation problems. It would be most desirable if the catalyst produced high yields of linearly-extended polyalkylenepolyamines, and simultaneously low yields of undesirable cyclic products.